1. Field of the Invention
The present invention relates to a technique for controlling optical zooming and electronic zooming of an imaging apparatus.
2. Description of the Related Art
Video cameras and digital cameras serving as imaging apparatuses are demanded to mount a high magnification zooming function to enable telephotography. To this end, various attempts have been made to achieve the high magnification zoom function by improving the performance of an optical zoom lens. However, generally, as the magnification of the optical zoom lens is increased, a lens system is increased in size and weight . In addition, the increase in size and weight tends to result in an increase in cost thereof. Thus, a method has been proposed, which achieves a high magnification by combining optical zoom for optically performing enlargement/reduction of an object image utilizing optical performance of a lens with electronic zoom for electronically performing enlargement/reduction of an image signal output from an image sensor.
For example, Japanese Patent Application Laid-Open No. 2000-184259 discusses the following method. That is, at a wide-angle end side, a zooming up operation is performed by increasing the magnification ratio of electronic zoom. When the magnification ratio reaches a certain value, optical zoom is started to move to a telephoto side to further perform a zooming up operation.
However, generally, in a case where images having the same number of pixels are generated, better image quality of the images is obtained by using more pixel-lines (hereunder sometimes referred to simply as lines) output from an image sensor. In view of this fact, technical ideas discussed in Japanese Patent Application Laid-Open No. 2000-184259 cause the following problem. That is, in a case where the optical zooming is used to perform zooming up, the number of lines to be extracted from the lines output from the image sensor satisfies the number of lines displayed in a monitor. However, then, the number of lines to be extracted therefrom becomes smaller. Therefore, the image quality of the image is degraded. This is because a zooming up operation is performed by increasing the magnification ratio of electronic zooming preferentially than the optical zooming up operation.